Radar sensors can be used for detecting a remote object as well as for measuring a distance and speed of an object. In this case, the measurement is carried out by means of an emission of radar radiation in the direction of the object and a detection of a reflection of the radar radiation at the object.
Radar sensors comprise, as a rule, a radar sensor element, which is arranged on an electric circuit board, the circuit board usually being enclosed by an opaque sensor housing. A precise alignment of the radar sensor element to a remote object is, however, difficult because of the opacity of the housing and possible irregularities in the positioning of the radar sensor element in the housing.
A radar sensor, in which a focal length is determined by the sensor housing and the lens, is known from DE 10 2012 20 29 13 A1. The precision of the focal length depends, further, on the tolerance of the housing and on the screw-in depth of the lens as well as on the fastening of the sensor circuit board.